3rd generation partnership project (3GPP) long-term evolution (LTE) is a technology for enabling high-speed packet communications. Many schemes have been proposed for the LTE objective including those that aim to reduce user and provider costs, improve service quality, and expand and improve coverage and system capacity. The 3GPP LTE requires reduced cost per bit, increased service availability, flexible use of a frequency band, a simple structure, an open interface, and adequate power consumption of a terminal as an upper-level requirement.
In the future versions of the LTE-A, it has been considered to configure low-cost/low-end (or, low-complexity) user equipments (UEs) focusing on the data communication, such as meter reading, water level measurement, use of security camera, vending machine inventory report, etc. For convenience, these UEs may be called machine type communication (MTC) UEs. Since MTC UEs have small amount of transmission data and have occasional uplink data transmission/downlink data reception, it is efficient to reduce the cost and battery consumption of the UE according to a low data rate. Specifically, the cost and battery consumption of the UE may be reduced by decreasing radio frequency (RF)/baseband complexity of the MTC UE significantly by making the operating frequency bandwidth of the MTC UE smaller.
As data traffic occurs occasionally rather than continuously for a MTC UE, regular measurement and reporting based channel estimation may not work very effectively. Moreover, once a MTC device has completed transmission of data, it is likely to go into sleep mode. Thus, it would be desirable to enable “one-time” reliable transmission rather than multiple transmissions based on acknowledgement/non-acknowledgement (ACK/NACK) process. Furthermore, it is expected that MTC devices will be installed in, e.g. basement, indoor, inside of buildings, etc., in which coverage may be limited. Thus, improving downlink and uplink coverage may be essential.
For the MTC UE, frequency hopping may be utilized. That is, frequency between transmissions may change. When the MTC UE needs to switch frequencies between transmissions, a method for handling frequency retuning effectively may be required.